DERATE

TRUCK

FAULT CODES

Truck fault codes

What every diesel truck SPN/FMI and OBD code means, the most likely cause, and the test that confirms it. Free, no account.

Aftertreatment / DPF

SPN 3251 FMI 0Particulate filter · The particulate filter is plugged and the engine is losing power.

Air intake / Turbo

P0299Turbo underboost · The turbo is not making the boost the engine asks for.
SPN 102 FMI 18Boost pressure · Intake manifold pressure is low: the truck is down on power.

Brakes / ABS

SPN 789 FMI 7Trailer ABS · ABS is disabled: the brakes still work, the assist does not.

Cooling

SPN 110 FMI 0High temperature · Coolant is running too hot: engine damage risk.

Electrical / J1939

SPN 639 FMI 2Data bus · The truck network is losing communication between modules.

Engine

SPN 1569 FMI 31Torque derate · The engine is deliberately limiting power.

Lubrication

SPN 100 FMI 1Oil pressure · Oil pressure is critically low: shut the engine down.

SCR / DEF

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